Three dimensional structures useful as cleaning sheets

ABSTRACT

Disclosed are cleaning sheets having substantial macroscopic three-dimensionality. Optionally, the macroscopically three-dimensional cleaning sheets can comprise a contractable material (e.g., a scrim material), which when heated and then cooled contracts so as to provide a macroscopic, three-dimensional structure. Macroscopic three-dimensionality is described in terms of “average peak-to-peak distance” and “surface topography index”, as well in terms of “average height differential”. Also disclosed are cleaning implements comprising a handle and the described cleaning sheets. Processes for the sheets, benefits of the processes, and articles of manufacture are also disclosed.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.11/089,411, filed Mar. 24, 2005, now abandoned, and of U.S. applicationSer. No. 11/091,223, filed Mar. 28, 2005, now abandoned, which arecontinuations of U.S. application Ser. No. 10/902,213, filed Jul. 29,2004, now U.S. Pat. No. 6,936,330, which is a continuation of U.S.application Ser. No. 09/881,473, filed Jun. 14, 2001, now U.S. Pat. No.6,797,357, which is a divisional of U.S. application Ser. No.09/082,396, filed May 20, 1998, now U.S. Pat. No. 6,561,354, whichclaims the benefit of U.S. Provisional Application Ser. No. 60/055,330,filed Aug. 12, 1997 and U.S. Provisional Application Ser. No.60/047,619, filed May 23, 1997.

FIELD OF THE INVENTION

This invention relates to cleaning sheets particularly suitable forremoval and entrapment of dust, lint, hair, sand, food crumbs, grass andthe like.

BACKGROUND OF THE INVENTION

The use of nonwoven sheets for dry dust-type cleaning are known in theart. Such sheets typically utilize a composite of fibers where thefibers are bonded via adhesive, entangling or other forces. See, forexample, U.S. Pat. No. 3,629,047 and U.S. Pat. No. 5,144,729. To providea durable wiping sheet, reinforcement means have been combined with thestaple fibers in the form of a continuous filament or network structure.See, for example, U.S. Pat. No. 4,808,467, U.S. Pat. No. 3,494,821 andU.S. Pat. No. 4,144,370. Also, to provide a product capable ofwithstanding the rigors of the wiping process, prior nonwoven sheetshave employed strongly bonded fibers via one or more of the forcesmentioned above. While durable materials are obtained, such strongbonding may adversely impact the materials' ability to pick up andretain particulate dirt. In an effort to address this concern, U.S. Pat.No. 5,525,397 to Shizuno et al. describes a cleaning sheet comprising apolymeric network layer and at least one nonwoven layer, wherein the twolayers are lightly hydroentangled so as to provide a sheet having a lowentanglement coefficient. The resulting sheet is said to providestrength and durability, as well as improved dust collecting performancebecause the composite fibers are lightly hydroentangled. Sheets having alow entanglement coefficient (i.e., not more than 500 m) are said tooffer better cleaning performance because a greater degree of fibers areavailable for contact with dirt.

While the sheets described in the '397 patent are alleged to addresssome of the problems with prior nonwoven cleaning sheets, those sheetsappear to be generally of a uniform basis weight, at least on amacroscopic level; and are essentially of a uniform caliper, again on amacroscopic level. That is, ordinary and expected basis weight andcaliper fluctuations and variations may occur on a random basis, as aresult of fluid pressure differentials during hydroentanglement.However, the structure would not be deemed to comprise discrete regionsthat differ with regard to basis weight. For example, if on amicroscopic level, the basis weight of an interstice between fibers weremeasured, an apparent basis weight of zero would result when, in fact,unless an aperture in the nonwoven structure was being measured, thebasis weight of such region is greater than zero. Such fluctuations andvariations are a normal and expected result of the hydroentanglingprocess. The skilled artisan would interpret nonwovens having suchvariations, including those described in the '397 patent, as havingessentially a uniform basis weight and caliper, in the macroscopicsense. The result of a sheet having a uniform basis weight is that thematerial is not particularly suitable for collecting and entrapping soilof a diverse size, shape, etc.

As such, there is a continuing need to provide cleaning sheets thatoffer improved soil removal. In this regard, Applicants have found thatby providing increased three-dimensionality, in the macroscopic sense,to cleaning sheets, enhanced soil removal is achieved.

Accordingly, it is an object of this invention to overcome the problemsof the prior art and particularly to provide a structure more capable ofremoving and entrapping various types of soil. Specifically, it is anobject of this invention to provide a nonwoven structure havingsignificant three-dimensionality, which is described in detail below.

It is another object to provide improved processes for cleaning anddesirable benefits for the consumer and user of the sheets, especiallyby packaging the sheets, either in roll form, with perforations forseparating sheets, or means for separating the sheets into usefullengths, and packaging them in packages that inform the consumer of theimproved processes and/or the benefits that can be obtained, especiallythose benefits that are not intuitively obvious to the consumer. It isanother object to provide cleaning sheets with additives, especiallythose that improve adherence of soil to the substrate, and especiallyfor those sheets described hereinafter with three dimensional structure,such combinations having special performance benefits, and suchcombinations providing improved benefits.

SUMMARY OF THE INVENTION

The present invention relates to a cleaning sheet having substantialmacroscopic three-dimensionality. As used herein, the term “macroscopicthree-dimensionality”, when used to describe three-dimensional cleaningsheets, means the three-dimensional pattern is readily visible to thenaked eye when the perpendicular distance between the viewer's eye andthe plane of the sheet is about 12 inches. In other words, thethree-dimensional structures of the present invention are cleaningsheets that are non-planar, in that one or both surfaces of the sheetexist in multiple planes, where the distance between those planes isobservable to the naked eye when the structure is observed from about 12inches. By way of contrast, the term “planar” refers to cleaning sheetshaving fine-scale surface aberrations on one or both sides, the surfaceaberrations not being readily visible to the naked eye when theperpendicular distance between the viewer's eye and the plane of the webis about 12 inches or greater. In other words, on a macroscale, theobserver would not observe that one or both surfaces of the sheet existin multiple planes so as to be three-dimensional.

The macroscopically three-dimensional structures of the presentinvention optionally comprise a scrim material, which when heated andthen cooled, contracts so as to provide a macroscopic three-dimensionalstructure. Other materials which provide contractile forces so as toprovide three-dimensionality are discussed below. Macroscopicthree-dimensionality is described herein in terms of “average heightdifferential”, which is defined herein as the average distance betweenadjacent peaks and valleys of a given surface of a sheet, as well as the“average peak-to-peak” distance, which is the average distance betweenadjacent peaks of a given surface. Macroscopic three-dimensionality isalso described in terms of the “Surface Topography Index” of the outwardsurface(s) of the cleaning sheet; Surface Topography Index is the ratioobtained by dividing the Average Height Differential of a surface by theAverage Peak to Peak Distance of that surface. In one embodiment, bothof the sheet's outward surfaces will have the described Average Peak toPeak Distance and Surface Topography properties. Methods for measuringAverage Peak to Peak Distance and Average Height Differential aredescribed in detail in the Test Method section, below.

The Average Peak to Peak Distance of at least one outward surface willbe at least about 1 mm, more preferably at least about 2 mm, and stillmore preferably at least about 3 mm In one embodiment, the Average Peakto Peak Distance is from about 1 to about 20 mm, particularly from about3 to about 16 mm, more particularly from about 4 to about 12 mm TheSurface Topography Index of at least one outward surface will be fromabout 0.01 to about 10, preferably from about 0.1 to about 5, morepreferably from about 0.2 to about 3, still more preferably from about0.3 to about 2. While the value of the Average Height Differential isnot critical, at least one outward surface will preferably have anAverage Height Differential of at least about 0.5 mm, more preferably atleast about 1 mm, and still more preferably at least about 1.5 mm TheAverage Height Differential of at least one outward surface willtypically be from about 0.5 to about 6 mm, more typically from about 1to about 3 mm.

The sheets of this invention and similar sheets, especially those thatcontain additives at low levels, as described herein, and especiallythose where the additive is substantially uniformly attached over atleast one continuous area, can be used in improved processes forcleaning and to provide desirable benefits for the consumer and user ofthe sheets, some of those benefits being ones that are not intuitivelyobvious to a consumer, as detailed hereinafter. It is thereforedesirable to package the sheets, either in roll form, with perforationsfor aiding in separating sheets, or with means for separating the sheetsinto useful lengths, and/or packaging them in packages that inform theconsumer of the improved processes and/or the benefits that can beobtained, especially those benefits that are not intuitively obvious tothe consumer. The cleaning sheets with additives, including those withdesirable low levels of such additives, preferably substantiallyuniformly attached, at least in one, or more areas, provide, incombination, special performance benefits, and such combinations canprovide improved benefits, especially when the sheets have the desirablestructures set forth herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view schematic illustration of a three layer embodimentof a cleaning sheet of the present invention, wherein the second layercomprises a scrim material having filaments which run parallel to theside and end edges of the sheet, wherein a portion of the first layer isshown cut away, and wherein surface features of the first layer areomitted for clarity.

FIG. 2 is an illustration of the type shown in FIG. 1 depicting analternative embodiment of the present invention wherein the filaments ofthe second layer are inclined at an angle of about 45 degrees relativeto the side and end edges of the cleaning sheet.

FIG. 3 is a plan view schematic illustration of the photograph of FIG. 5showing the texture of the macroscopically three-dimensional outersurface of the first layer, and particularly the extended ridges on theouter surface of the first layer.

FIG. 4 is a cross-sectional illustration of the sheet taken parallel toone of the filaments of the second layer and showing portions of thefilament extending intermediate the filament intersections, the portionsof the filament that are not bound to the first layer, as well asportions of the filaments extending intermediate the filamentintersections which are not bound to the third layer.

FIG. 5 is a photomicrograph showing the texture of the macroscopicallythree dimensional surface of the first layer, and in particular theelongated ridges of the surface. The scale in FIG. 5 is in inches.

FIG. 6 is a enlarged photomicrograph of the type shown in FIG. 5 showingan elongated ridge having branches extending in different directions.

FIG. 7 is a Scanning Electron Micrograph providing a perspective view ofthe macroscopically three dimensional surface of the first layer.

FIG. 8 is a Scanning Electron Micrograph of a cross-section of thecleaning sheet showing portions of filaments extending intermediatefilament intersections, which portions of the filaments are unbonded tothe first layer.

FIG. 9 is a Scanning Electron Micrograph showing bonding of the firstand third layers to the second layer at the filament intersections.

DETAILED DESCRIPTION OF THE INVENTION I. Definitions

As used herein, the term “comprising” means that the various components,ingredients, or steps, can be conjointly employed in practicing thepresent invention. Accordingly, the term “comprising” encompasses themore restrictive terms “consisting essentially of” and “consisting of”.

As used herein, the term “hydroentanglement” means generally a processfor making a material wherein a layer of loose fibrous material (e.g.,polyester) is supported on an apertured patterning member and issubjected to water pressure differentials sufficiently great to causethe individual fibers to entangle mechanically to provide a fabric. Theapertured patterning member can be formed, e.g., from a woven screen, aperforated metal plate, etc.

As used herein, the term “Z-dimension” refers to the dimensionorthogonal to the length and width of the cleaning sheet of the presentinvention, or a component thereof. The Z-dimension usually correspondsto the thickness of the sheet.

As used herein, the term “X-Y dimension” refers to the plane orthogonalto the thickness of the cleaning sheet, or a component thereof. The Xand Y dimensions usually correspond to the length and width,respectively, of the sheet or a sheet component.

As used herein, the term “layer” refers to a member or component of acleaning sheet whose primary dimension is X-Y, i.e., along its lengthand width. It should be understood that the term layer is notnecessarily limited to single layers or sheets of material. Thus thelayer can comprise laminates or combinations of several sheets or websof the requisite type of materials. Accordingly, the term “layer”includes the terms “layers” and “layered.”

For purposes of the present invention, an “upper” layer of a cleaningsheet is a layer that is relatively further away from the surface thatis to be cleaned (i.e., in the implement context, relatively closer tothe implement handle during use). The term “lower” layer converselymeans a layer of a cleaning sheet that is relatively closer to thesurface that is to be cleaned (i.e., in the implement context,relatively further away from the implement handle during use).

All percentages, ratios and proportions used herein are by weight unlessotherwise specified.

II. Cleaning Sheets

The present invention relates to a cleaning sheet useful for removingdust, lint, hair, grass, sand, food crumbs and other matter of varioussize, shape, consistency, etc., from a variety of surfaces. Preferably,the cleaning sheets will demonstrate improved cleaning performance inconsumer panel testing.

As a result of the ability of the cleaning sheets to reduce, oreliminate, by various means, including contacting and holding, dust,lint and other airborne matter from surfaces, as well as from the air,the sheets will provide greater reduction in the levels of suchmaterials on surfaces and in the atmosphere, relative to other productsand practices for similar cleaning purposes. This ability is especiallyapparent in sheets containing additives as described herein. Even thesheets of U.S. Pat. No. 5,525,397, incorporated hereinbefore, canprovide this benefit, albeit to a lesser extent than the preferredstructures herein, and therefore it is important to provide thisinformation on the package, or in association with the package, so as toencourage the use of the sheets, including those of the said '397patent, especially on non-traditional surfaces like walls, ceilings,upholstery, drapes, rugs, clothing, etc., where dusting sheets have notnormally been used. The use of a low level of additive, uniformlyattached on at least one, preferably continuous area of the sheet in aneffective amount to improve the adherence of soil, especiallyparticulates, and especially those particulates that provoke an allergicreaction, provides a surprising level of control over soil adherence. Atleast in those areas where the additive is present on the sheet, the lowlevel is important for such use, since, unlike traditional dustingoperations where oils are applied as liquids, or as sprays, there ismuch less danger of creating a visible stain, especially on suchnon-traditional surfaces, when the sheet is used. The preferredstructures also provide benefits by trapping larger particles ratherthan abrading them to smaller sizes.

Consumers with allergies especially benefit from the use of the sheetsherein, especially the preferred structures, since allergens aretypically in dust form and it is especially desirable to reduce thelevel of small particles that are respirable. For this benefit, it isimportant to use the sheets on a regular basis, and not just when thesoil becomes visually apparent, as in prior art procedures.

The cleaning sheets of the present invention can be made using either awoven or nonwoven process, or by forming operations using meltedmaterials laid down on forms, especially in belts, and/or by formingoperations involving mechanical actions/modifications carried out onfilms. The structures are made by any number of methods, once theessential three dimensional requirements are known. However, thepreferred structures are nonwoven, and especially those formed byhydroentanglement as is well known in the art, since they provide highlydesirable open structures. Therefore, preferred cleaning sheets usefulherein are nonwoven structures having the characteristics describedherein. Materials particularly suitable for forming the preferrednonwoven cleaning sheet of the present invention include, for example,natural cellulosics as well as synthetics such as polyolefins (e.g.,polyethylene and polypropylene), polyesters, polyamides, syntheticcellulosics (e.g., RAYON®), and blends thereof. Also useful are naturalfibers, such as cotton or blends thereof and those derived from variouscellulosic sources. Preferred starting materials for making thehydroentangled fibrous sheets of the present invention are syntheticmaterials, which can be in the form of carded, spunbonded, meltblown,airlaid, or other structures. Particularly preferred are polyesters,especially carded polyester fibers. The degree of hydrophobicity orhydrophilicity of the fibers is optimized depending upon the desiredgoal of the sheet, either in terms of type of soil to be removed, thetype of additive that is provided, when an additive is present,biodegradability, availability, and combinations of such considerations.In general, the more biodegradable materials are hydrophilic, but themore effective materials tend to be hydrophobic.

The cleaning sheets can be formed from a single fibrous layer, butpreferably are a composite of at least two separate layers. Preferably,the sheets are nonwovens made via a hydroentangling process. In thisregard, prior to hydroentangling discrete layers of fibers, it may bedesired to slightly entangle each of the layers prior to joining thelayers by entanglement.

In a particularly preferred embodiment of the present invention, toenhance the integrity of the final sheet, it is preferred to include apolymeric net (referred to herein as a “scrim” material) that isarranged with the fibrous material, e.g., though lamination via heat orchemical means such as adhesives, through hydroentanglement, etc. Scrimmaterials useful herein are described in detail in U.S. Pat. No.4,636,419, which is incorporated by reference herein. The scrims can beformed directly at the extrusion die or can be derived from extrudedfilms by fibrillation or by embossing, followed by stretching andsplitting. The scrim can be derived from a polyolefin such aspolyethylene or polypropylene, copolymers thereof, poly(butyleneterephthalate), polyethylene terephthalate, Nylon 6, Nylon 66, and thelike. Scrim materials are available from various commercial sources. Apreferred scrim material useful in the present invention is apolypropylene scrim, available from Conwed Plastics (Minneapolis,Minn.).

In another aspect of the present invention, Applicants have alsodiscovered that the incorporation of the scrim material into a cleaningsheet, followed by heating, provides macroscopic three-dimensionalcharacter to the sheet. This macroscopic three-dimensionality has beenfound to greatly enhance cleaning performance of the cleaning sheet,even where the basis weight of the sheet is essentially uniform. Inparticular, macroscopic three-dimensionality is achieved when thescrim/fiber composite is subjected to heating, then cooling. Thisprocess results in shrinkage (in the X-Y dimension) of the scrim and, asa result of its being attached with the fibers, provides a sheet withgreater three-dimensionality. The degree of added three-dimensionalityis controlled by the level of heating applied to the scrim/cleaningcombination. The inclusion of a scrim is particularly beneficial whenthe fiber aspect of the structure is a nonwoven, particularly when thestructure is hydroentangled.

In this aspect, the invention relates to macroscopicallythree-dimensional cleaning sheets. These sheets are preferablyrelatively open structures compared to, e.g., paper towels. In onepreferred embodiment, the macroscopically three-dimensional cleaningsheets have a first surface and a second surface and comprise a scrimmaterial. In one such preferred embodiment, the cleaning sheet has afirst outward surface and a second outward surface and comprises a scrimmaterial, wherein the Average Peak to Peak Distance of at least oneoutward surface is at least about 1 mm and the Surface Topography Indexof that surface(s) is from about 0.01 to about 5.

Regardless of the configuration of the cleaning sheets, the Average Peakto Peak Distance of at least one outward surface will be at least about1 mm, more preferably at least about 2 mm, and still more preferably atleast about 3 mm In one embodiment, the Average Peak to Peak distance isfrom about 1 to about 20 mm, particularly from about 3 to about 16 mm,more particularly from about 4 to about 12 mm The Surface TopographyIndex of at least one outward surface will be from about 0.01 to about10, preferably from about 0.1 to about 5, more preferably from about 0.2to about 3, still more preferably from about 0.3 to about 2. While notcritical, at least one outward surface will preferably have an AverageHeight Differential of at least about 0.5 mm, more preferably at leastabout 1 mm, and still more preferably at least about 1.5 mm The AverageHeight Differential of at least one outward surface will typically befrom about 0.5 to about 6 mm, more typically from about 1 to about 3 mm.

Again with regard to the macroscopic three-dimensional cleaning sheetsof the present invention, these structures will provide enhancedelongation, particularly in the CD direction, that will improve theirconformability, whether used as a stand alone product or when used incombination with a cleaning implement. In this regard themacroscopically three-dimensional sheets will preferably have a CDelongation value at 500 g of at least about 3%, more preferably at leastabout 6%, more preferably at least about 10%, still more preferably atleast about 15%, and still more preferably 20%.

The cleaning performance of any of the cleaning sheets of the presentinvention can be further enhanced by treating the fibers of the sheet,especially surface treating, with any of a variety of additives,including surfactants or lubricants, that enhance adherence of soils tothe sheet. When utilized, such additives are added to the cleaning sheetat a level sufficient to enhance the ability of the sheet to adheresoils. Such additives are preferably applied to the cleaning sheet at anadd-on level of at least about 0.01%, more preferably at least about0.1%, more preferably at least about 0.5%, more preferably at leastabout 1%, still more preferably at least about 3%, still more preferablyat least about 4%, by weight. Typically, the add-on level is from about0.1 to about 25%, more preferably from about 0.5 to about 20%, morepreferably from about 1 to about 15%, still more preferably from about 3to about 10%, still more preferably from about 4 to about 8%, and mostpreferably from about 4 to about 6%, by weight. A preferred additive isa wax or a mixture of an oil (e.g., mineral oil, petroleum jelly, etc.)and a wax. Suitable waxes include various types of hydrocarbons, as wellas esters of certain fatty acids (e.g., saturated triglycerides) andfatty alcohols. They can be derived from natural sources (i.e., animal,vegetable or mineral) or can be synthesized. Mixtures of these variouswaxes can also be used. Some representative animal and vegetable waxesthat can be used in the present invention include beeswax, carnauba,spermaceti, lanolin, shellac wax, candelilla, and the like.Representative waxes from mineral sources that can be used in thepresent invention include petroleum-based waxes such as paraffin,petrolatum and microcrystalline wax, and fossil or earth waxes such aswhite ceresine wax, yellow ceresine wax, white ozokerite wax, and thelike. Representative synthetic waxes that can be used in the presentinvention include ethylenic polymers such as polyethylene wax,chlorinated naphthalenes such as “Halowax,” hydrocarbon type waxes madeby Fischer-Tropsch synthesis, and the like.

When a mixture of mineral oil and wax is utilized, the components willpreferably be mixed in a ratio of oil to wax of from about 1:99 to about7:3, more preferably from about 1:99 to about 1:1, still more preferablyfrom about 1:99 to about 3:7, by weight. In a particularly preferredembodiment, the ratio of oil to wax is about 1:1, by weight, and theadditive is applied at an add-on level of about 5%, by weight. Apreferred mixture is a 1:1 mixture of mineral oil and paraffin wax.

Particularly enhanced cleaning performance is achieved when macroscopicthree-dimensionality and additive are provided in a single cleaningsheet. As discussed hereinbefore, these low levels are especiallydesirable when the additives are applied at an effective level andpreferably in a substantially uniform way to at least one discretecontinuous area of the sheet. Use of the preferred lower levels,especially of additives that improve adherence of soil to the sheet,provides surprisingly good cleaning, dust suppression in the air,preferred consumer impressions, especially tactile impressions, and, inaddition, the additive can provide a means for incorporating andattaching perfumes, pest control ingredients, antimicrobials, includingfungicides, and a host of other beneficial ingredients, especially thosethat are soluble, or dispersible, in the additive. These benefits are byway of example only. Low levels of additives are especially desirablewhere the additive can have adverse effects on the substrate, thepackaging, and/or the surfaces that are treated.

The application means for these additives preferably applies at least asubstantial amount of the additive at points on the sheet that are“inside” the sheet structure. It is an especial advantage of the threedimensional structures that the amount of additive that is in contactwith surface to be treated, and/or the package, is limited, so thatmaterials that would otherwise cause damage, or interfere with thefunction of the other surface, can only cause limited, or no, adverseeffects. The presence of the additive inside the structure is verybeneficial in that soil that adheres inside the structure is much lesslikely to be removed by subsequent wiping action.

FIG. 1 illustrates a multiple layer cleaning sheet 20 according to thepresent invention. The cleaning sheet 20 includes side edges 22 and endedges 24. The side edges 22 extend generally parallel to the length ofthe sheet 20, and the end edges 24 extend generally parallel to thewidth of the sheet. Optionally, the sheet 20 can include an edge seal 26extending around the perimeter of the sheet. Such an edge seal 26 can beformed by heating, by use of adhesives, or by a combination of heatingand adhesives.

The cleaning sheet 20 includes a first layer 100 and a second layer 200.Preferably, the cleaning sheet also includes a third layer 300. Thesecond layer 200 can be disposed between the first layer 100 and thethird layer 300. In FIG. 1, a portion of the first layer 100 is showncut away to reveal underlying portions of the second layer 200 and thethird layer 300.

The first layer 100 can be formed from woven materials, nonwovenmaterials, paper webs, foams, battings, and the like such as are knownin the art. Particularly preferred materials are nonwoven webs havingfibers or filaments distributed randomly as in “air-laying” or certain“wet-laying” processes, or with a degree of orientation, as in certain“wet-laying” and “carding” processes. The fibers or filaments of thefirst layer 100 can be natural, or of natural origin (e.g. cellulosicfibers such as wood pulp fibers, cotton linters, rayon, and bagassefibers) or synthetic (e.g. polyolefins, polyamides or polyesters). Thethird layer 300 can be substantially the same as the first layer 100, oralternatively, can be of a different material and/or construction.

In one embodiment, the first layer 100 and the third layer 300 can eachcomprise a hydroentangled web of synthetic nonwoven fibers having adenier of less than about 4.0, preferably less than about 3.0, morepreferably less than about 2.0 grams, per 9000 meter of fiber length. Asuitable first layer 100 (as well as a suitable third layer 300) is ahydroentangled web of polyester fibers having a denier of about 1.5grams or less per 9000 meters of fiber length, and the web having abasis weight of about 30 grams per square meter. A suitable web isavailable from PGI Nonwovens of Benson, N.C. under the designation PGI9936.

The second layer 200 is joined in a discontinuous manner to the firstlayer 100 (and to third layer 300 when present), and provides gatheringof the first layer by contraction of the second layer. Contractionmechanisms include, but are not limited to, heat contraction and elasticproperties of the second layer. As discussed above, in one suchembodiment, the second layer 200 comprises a net-like arrangement offilaments having openings defined by adjacent filaments. Alternatively,the second layer could be in the form of a polymeric film, which canoptionally have openings therethrough; to provide the requisitecontraction mechanism, such films must have sufficient elasticity toprovide the gathering function that results in surface threedimensionality. The film can be embossed so as to provide surfacedepressions instead of or in addition to openings. In anotheralternative, the contractile effects can be generated by inclusion offibers that contract upon heating and recooling. In this approach,certain of the fibers will not shrink, but because they are mechanicallyassociated to the shrinkable fibers, the entire sheet will “pucker” oncontraction of the shrinkable fibers, so long as such fibers areincluded at a sufficient level.

In the embodiments illustrated, the second layer comprises a net likearrangement of filaments including a first plurality of filaments 220and a second plurality of filaments 240. The filaments 220 extendgenerally parallel to one another, and the filaments 240 extendgenerally parallel to one another and generally perpendicular to thefilaments 220. The filaments extend between filament intersections 260.The intersecting, adjacent filaments 220 and 240 define openings 250 inthe second layer 200. The filament intersections and openings 250 arearranged in a generally nonrandom, repeating grid-like pattern.

The second layer 200 can comprise a polymeric net (referred to herein asa “scrim material”). Suitable scrim materials are described in U.S. Pat.No. 4,636,419 incorporated herein by reference. The scrim can be derivedfrom a polyolefin such as polyethylene or polypropylene, or copolymersthereof, poly(butylene terephthalate), polyethylene terephthalate, Nylon6, Nylon 66, and the like, and mixtures thereof.

The scrim material is preferably joined to the layers 100 and 300through lamination via heat or chemical means such as adhesives.Preferably, the filaments of the scrim material contract relative to thelayers 100 and 300 upon heating, such that contraction of the secondlayer 200 gathers the layers 100 and 300, and imparts a macroscopicthree dimensional texture to the outer surfaces of the layers 100 and300, as is described in more detail below.

A particularly suitable scrim material useful as the second layer 200 isa heat activated reinforcing netting available from Conwed Plastics ofMinneapolis, Minn. as THERMANET brand reinforcing netting, having apolypropylene/EVA resin, 2 sided adhesive, and a filament count of 3filaments per inch by 2 filaments per inch prior to contraction such asby heating. After heating, the second layer 200 can have between about3.5 to 4.5 filaments per inch by between about 2.5 to 3.5 filaments perinch.

By “2 sided adhesive” it is meant that the EVA adhesive (Ethyl-VinylAcetate adhesive) is present on both sides of the filaments. Theactivation temperature of the EVA is generally about 85° C. (about 185°F.). During lamination of the layer 200 to the polyester fibers of thelayers 100 and 300, the EVA adhesive is activated to provide bondingbetween the filaments of the layer 200 and the fibers of the layers 100and 300. Without being limited by theory, it is believed that pressingat a relatively low pressure (e.g. less than 50 psi and more preferablyless than 25 psi) for a relatively short time (e.g. less than about 30seconds), the filaments of the layer 200 are not continuously bonded tothe nonwovens of layers 100 and 300. This discontinuous bonding, alongwith the shrinkage of the polypropylene filaments upon heating, providesenhanced texture of the outward surfaces of layers 100 and 300.

In FIG. 1, the filaments 220 extend generally parallel to the side edges22 and to the length of the sheet 20. Likewise, the filaments 240 extendgenerally parallel to the end edges 24 and to the width of the sheet 20.

Alternatively, the filaments 220 can be inclined at an angle of betweenabout 20 and about 70 degrees with respect to the length of the sheet 20and the side edges 22, and more preferably between about 30 degrees andabout 60 degrees. The filaments 240 can be inclined at an angle ofbetween about 20 and about 70 degrees with respect to the width of thesheet 20 and the end edges 24, and more preferably between about 30degrees and about 60 degrees.

FIG. 2 shows an embodiment of the present invention wherein thefilaments 220 are inclined at an angle of about 45 degrees with respectto the side edges 22 (Angle A in FIG. 2), and wherein the filaments 240are inclined at an angle of about 45 degrees with respect to the endedges 24 (Angle B in FIG. 2). Such an arrangement provides the advantagethat the angled orientation of the filaments 220 and 240 with respect tothe length and width of the sheet 20 permits deformation of the netstructure of layer 200 parallel to the edges 22 and 24. Such deformationprovides the sheet with elastic like behavior parallel to the length andwidth of the sheet.

By “elastic like behavior” it is meant that the element in question canbe elongated under tension in a direction to have an elongated dimensionmeasured in that direction which is at least 120 percent of theelement's original, relaxed dimension in that direction, and that uponrelease of the elongating tension the element recovers to within 10percent of its relaxed dimension.

An important aspect of one embodiment of the present invention is thatthe first layer 100 is intermittently bonded to the second layer 200. Inparticular, the first layer 100 can be intermittently bonded to thesecond layer 200 at the filament intersections 260, while portions ofthe filaments 220, portions of the filaments 240, or portions of boththe filaments 220 and 240 intermediate the filament intersections 260remain unbonded to the first layer 100.

As a result, the surface texture of the outer surface of the first layer100 is not limited by the geometry of the openings in the net-likearrangement of filaments, but rather, is decoupled from the repeating,nonrandom geometry of the openings 250. Similarly, the third layer 300can be intermittently bonded to the second layer 200 to provide similarsurface texture to the outer surface of the third layer 300.

The surface texture of the first layer 100 is omitted in FIGS. 1 and 2for clarity. The surface texture is shown in FIGS. 3-8.

FIG. 3 provides a schematic illustration of the surface texture of firstlayer 100 shown in the photograph of FIG. 5. FIG. 4 provides across-sectional illustration of the surface texture of the first layer100 and the third layer 300. FIG. 5 is a photomicrograph showing thetexture of the macroscopically three dimensional surface of the firstlayer 100. FIG. 6 is a photomicrograph showing the three dimensionalsurface of the first layer 100 enlarged. FIG. 7 is a scanning electronmicrograph providing a perspective view of the three dimensional surfaceof the first layer 100. FIG. 8 is a scanning electron micrograph of across-section of the sheet.

Referring to FIGS. 3-8, portions of the first layer 100 are gathered bycontraction of the second layer 200 relative to the first layer 100.This gathering provides the first layer 100 with a macroscopically threedimensional surface as illustrated in FIG. 3-8. Likewise, the thirdlayer 300 can be gathered by contraction of the second layer 200 toprovide the third layer 300 with a macroscopically three dimensionalsurface.

The three dimensional surface of the first layer 100 has relativelyelevated peaks 105 and relatively depressed valleys 107. The third layerhas peaks 305 and valleys 307. In FIG. 4, the peaks of layer 100 areindicated with reference numbers 105A and 105B, and the valleys of layer100 are indicated with reference numbers 107A and 107B. Similarly, thepeaks of layer 300 are labeled 305A and 305B, and the valleys arelabeled 307A and 307B. The peaks 105 provide elongated ridges 120 on theoutward surface of the first layer 100, and the peaks 305 provideelongated ridges 320 on the outward surface of the third layer 300.

The macroscopic three-dimensionality of the outer surface of the firstlayer 100 can be described in terms of the “Average Height Differential”of a peak and an adjacent valley, as well as in terms of the “AveragePeak-to-Peak Distance” between adjacent peaks. The height differentialwith respect to a peak 105A/valley 107A pair is the distance H in FIG.4. The peak-to-peak distance between an adjacent pair of peaks 105A and105B is indicated as distance D in FIG. 4. The “Average HeightDifferential” and the “Average Peak-to-Peak Distance” for the sheet aremeasured as set forth below in “Test Methods.” The “Surface TopographyIndex” of the outward surface is the ratio obtained by dividing theAverage Height Differential of the surface by the Average Peak to PeakDistance of the surface.

It will be apparent to one skilled in the art that there will berelatively small regions of peaks and valleys that are not significantenough to be considered as providing macroscopic three dimensionality.For example, such regions can exist in the element(s) that is eventuallycontracted by, for example, an elastic material to providethree-dimensionality. Again, such fluctuations and variations are anormal and expected result of the manufacturing process and are notconsidered when measuring Surface Topography Index.

Without being limited by theory, it is believed that the SurfaceTopography Index is a measure of the effectiveness of themacroscopically three dimensional surface in receiving and containingmaterial in the valleys of the surface. A relatively high value ofAverage Height Differential for a given Average Peak to Peak Distanceprovides deep, narrow valleys which can trap and hold materials.Accordingly, a relatively high value of Surface Topography Index isbelieved to indicate effective capture of materials during wiping.

The cleaning sheets of the present invention have the characteristicthat portions of the filaments 220, portions of the filaments 240, orportions of both the filaments 220 and 240 of the second layer 200 arenot bonded to the first layer 100. Referring to FIG. 4, a portion of afilament 220 extending intermediate filament intersections 260A and 260Bis not bonded to the first layer 100. The portion of the filament 220which is not bonded to the first layer 100 is indicated by referencenumber 220U. A gap between the filament 220 and the first layer 100provides a void space 180 intermediate the first layer 100 and thefilament 220. Similarly, portions of the filament 220 extendingintermediate filament intersections 260 are not bonded to the thirdlayer 300, thereby providing a void space 380 intermediate the thirdlayer 300 and the filament 220.

FIGS. 7 and 8 also illustrate this characteristic of the sheet 20. InFIG. 7, elongated ridges 120 and 320 are visible on the outward surfacesof both the first and third layers 100, 300, respectively. In FIG. 8, afilament 220 is seen extending between two filament intersections 260.The portion of the filament extending between the two filamentintersections is spaced from, and not bonded to, the first layer.

Ridges 120 are shown in plan view in FIG. 3 and FIG. 5. At least some ofthe ridges 120 extend across at least one filament of the second layer200. In FIG. 4, the ridge 120 corresponding to peak 105A extends acrossat least one filament 220.

Because the ridges extend across one or more filaments, the ridges canhave a length greater than the maximum distance between adjacentfilament intersections 260 (the distance between adjacent filamentintersections after contraction of layer 200 and gathering of layers 100and 300). In particular, the length of the ridges 120 can be greaterthan the maximum dimension of the openings 250 in FIG. 1 (i.e. greaterthan the length of the diagonal extending across the rectangularopenings 250). The length of a ridge 120 is indicated by the letter L inFIG. 3. The Length L is the straight line distance between two ends of aridge 120, the ends of the ridge 120 being those points where a ridge120 terminates at a valley 107.

The value of L can be at least about 1.0 centimeter, more particularlyat least about 1.5 centimeter for some of the ridges 120. In oneembodiment, at least some of the ridges 120 have a length L of at leastabout 2.0 centimeters. The length L can be at least twice the distancebetween adjacent filament intersections.

For instance, in order to determine the length of ridges 120 relative tothe distance between adjacent filament intersections, the cleaning sheet20 can be wetted and positioned on a light table or other suitablesource of back lighting. Such back lighting, in combination with wettingof the cleaning sheet, can be used to make the filament intersections ofthe layer 200 visible through the layer 100, so that the lengths ofridges 120 relative to the distance between filament intersections canbe measured with a scale.

The elongated ridges provide soft, deformable wiping elements forenhanced removal of material from the surface being cleaned. Incontrast, if the filaments of the second layer were continuously bondedto the first and second layers, then any texture features of the firstand third layers would be confined to the area associated with theopenings 250 in the second layer 200.

At least some of the elongated ridges extend in a direction differentfrom at least some of the other ridges. Referring to FIG. 3, the ridges120A, 120B, and 120C each extend in a different direction. Accordingly,the sheet is effective in picking up material when the sheet is used towipe in different directions.

FIGS. 3 and 6 also illustrate that at least some of the ridges 120 canhave branches extending in different directions. In FIG. 3, a ridge 120is shown having three branches 123A, 123B, and 123C extending indifferent directions. Likewise, FIG. 6 shows a ridge 120 having at leastthree branches labeled 123A, 123B, and 123C.

The first layer 100 and the third layer 300 are securely bonded to thesecond layer 200 at the filament intersections 260. FIG. 9 illustratesthe bonding of fibers of both the layers 100 and 300 to the second layerat a filament intersection 260.

Referring to FIGS. 4, 7 and 8, the peaks 105 of the first layer 100 aregenerally offset from the peaks 305 of the third layer in the plane ofthe sheet 20. For instance, in FIG. 4 the peak 305A of the third layerdoes not directly underlie the peak 105A, but instead is generallyaligned with the valley 107A associated with peak 105A. Accordingly, thepeaks 105 of the first layer are generally aligned with valleys 307 ofthe third layer, and the peaks 305 of the third layer are generallyaligned with valleys 107 of the first layer.

The present invention also includes a method for making a multiple layercleaning sheets. A first nonwoven layer, a second layer comprising a netlike arrangement of filaments, and a third nonwoven layer are provided.The first layer is positioned adjacent an upper surface of the secondlayer, in face to face relationship with the second layer. The thirdlayer is positioned adjacent a lower surface of the second layer, inface to face relationship with the second layer.

The first layer and the third layer are then intermittently bonded todiscrete, spaced apart portions of the second layer, such that portionsof the filaments extending between filament intersections remainunbonded to the first layer, and such that portions of the filamentsextending between filament intersections remain unbonded to the thirdlayer. The second layer is contracted relative to the first layer andthe third layer to provide a gathered, macroscopically three dimensionaloutward surface of the first layer, and a gathered, macroscopicallythree dimensional outward surface of the third layer. The steps ofbonding and contracting can occur simultaneously, or in sequence.

The step of intermittently bonding the second layer to the first layerand the third layer can comprise the step of heated pressing of thefirst layer, the second layer, and third layer at a relatively lowpressure for a relatively short time period to avoid relativelycontinuous bonding of the second layer to the first and third layers.

In one embodiment, the three layers can be joined using a BASIX B400hand press manufactured by the HIX Corp. of Pittsburg, Kans. The threelayers are joined by pressing in the hand press at a temperature ofabout 330° F. for about 13 seconds. The hand press has an adjustment forvarying the clearance, and hence the pressure, provided in the press.The adjustment can be varied as desired to provide the desired texturein the layers 100 and 300.

The invention also comprises packages containing cleaning sheets, thepackages being in association with information that will inform theconsumer, by words and/or by pictures, that use of the sheets willprovide cleaning benefits which include soil (e.g., dust, lint, etc.)removal and/or entrapment and this information can comprise the claim ofsuperiority over other cleaning products. In a highly desirablevariation, the package bears the information that informs the consumerthat the use of the cleaning sheet provides reduced levels of dust andother airborne matter in the atmosphere. It is very important that theconsumer be advised of the potential to use the sheets onnon-traditional surfaces, including fabrics, pets, etc., to ensure thatthe full benefits of the sheets is realized. Accordingly, the use ofpackages in association with information that will inform the consumer,by words and/or by pictures, that use of the compositions will providebenefits such as improved cleaning, reduction of particulate soil in theair, etc. as discussed herein, is important. The information caninclude, e.g., advertising in all of the usual media, as well asstatements and icons on the package, or the sheet itself, to inform theconsumer.

The prior products which do not comprise the preferred structures hereincan be used to provide the benefits in a lesser degree, and to theextent that these benefits have not been previously recognized, theyshould be included in the information provided. Otherwise, the consumerwill not obtain the full value of the improved performance relative toconventional products or practices.

III. Cleaning Implements

In another aspect, the present invention relates to a cleaning implementcomprising the cleaning sheets discussed above. In this regard, thecleaning implement comprises:

-   -   a. a handle; and    -   b. a removable cleaning sheet having a first surface and a        second surface, wherein the Average Peak to Peak Distance is at        least about 1.0 mm and the Surface Topography Index is from        about 0.01 to about 5.

The implement and, separately, the cleaning sheet of the presentinvention are designed to be compatible with all hard surfacesubstrates, including wood, vinyl, linoleum, no wax floors, ceramic,FORMICA®, porcelain, and the like.

The handle of the cleaning implement comprises any elongated, durablematerial that will provide ergonomically practical cleaning. The lengthof the handle will be dictated by the end-use of the implement.

The handle will preferably comprise at one end a support head to whichthe cleaning sheet can be releasably attached. To facilitate ease ofuse, the support head can be pivotably attached to the handle usingknown joint assemblies. Any suitable means for attaching the cleaningsheet to the support head can be utilized, so long as the cleaning sheetremains affixed during the cleaning process. Examples of suitablefastening means include clamps, hooks & loops (e.g., VELCRO®), and thelike. In a preferred embodiment, the support head will comprise meansfor gripping the sheet on it's upper surface to keep the sheetmechanically attached to the head during the rigors of cleaning.However, the gripping means will readily release the sheet forconvenient removal and disposable.

The cleaning sheets useful in the cleaning implement of the presentinvention are as described above.

IV. Test Methods

A. Average Height Differential

Average Height Differential is determined using a light microscope(e.g., Zeiss Axioplan, Zeiss Company, Germany) equipped with aZ-dimension measuring device (e.g., Microcode II, sold by Boeckeler,Instruments). This procedure involves locating a peak or valley regionof the sheet, focusing the microscope and zeroing the Z-dimensionmeasuring device. The microscope is then moved to an adjacent valley orpeak region, respectively, and the microscope is refocused. The displayof the instrument indicates the height difference between thispeak/valley or valley/peak pair. This measurement is repeated at least10 times, at random locations on the sheet, and the Average HeightDifferential is the average of these measurements.

B. Peak-to-Peak Distance

Simple light microscopy can be used to measure peak-to-peak distance.The magnification used should be sufficient to readily measure thedistance between two adjacent peaks. This measurement is repeated atleast 10 times, at random locations on the sheet, and the AveragePeak-to-Peak Distance is the average of these measurements.

C. CD Elongation at 500 g

CD elongation is a measure of the percent elongation a test sampleexhibits under a load of 500g. CD Elongation can be measured using aSintech Renew Instron 7310 (including the Testworks software package)with a 100N load cell. Using this instrument, a Load vs. % Strain curveis generated. The testing parameters are as follows:

Sample width=30 mm

Gauge Length=100 mm

Crosshead speed=300 mm/min

From the curve generated, the software obtains the % Strain (%Elongation) at a load of 500 g. This is reported as CD Elongation at 500g.

V. Representative Examples

The following are illustrative examples of cleaning sheets of thepresent invention. Enhanced three dimensionality is indicated in TableI.

Example 1

This example illustrates the combination of carded webs and a scrim(i.e., a net of polypropylene filament) to make a cleaning sheet of thepresent invention. Two carded polyester fiber webs with a scrim inbetween is prepared. The combination of the two carded webs and thescrim are then placed on top of an apertured forming belt (N 50 flatsquare) and are hydroentangled and dried. The water entangling processcauses the fibers to become intertangled and to also become intertangledwith the scrim, while causing the fibers to move apart and provide twodistinct basis weight regions. During the drying process, thehydroentangled sheet becomes “quilted” (i.e., greater threedimensionality is achieved) as a result of shrinkage of thepolypropylene scrim relative to the polyester nonwoven. As a preferredoptional step, the nonwoven sheet is surface coated (by, e.g., printing,spraying, etc.) with 5%, by weight, of a 1:1 mixture of mineral oil andparaffin wax. The entangled nonwoven sheet is subjected to furtherheating, for example in a press at 180° C. for 10 sec, to provide agreater degree of three dimensionality. This sheet is designated asExample 1 in Table 1. (This heating can may be performed before or afteradding the optional surface treatment, but is preferably conducted priorto application of the additive.) This additional heating provides evenfurther enhanced three-dimensionality.

Example 2

A cleaning sheet according to the present invention includes a firstlayer 100, a second layer 200, and a third layer 300. The first layer100 and the third layer 300 each comprise a hydroentangled web ofpolyester fibers having a basis weight of about 30 grams per squaremeter. The second layer comprises the above described THERMANET® brandreinforcing netting having a polypropylene/EVA resin, 2 sided adhesive,and a filament count of 3 filaments per inch by 2 filaments per inchprior to contraction of the second layer. The second layer 200 ispositioned between the first layer 100 and the third layer 300 in aBASIX B400 hand press. The three layers are joined by pressing in thehand press at a temperature setting of about 330° F. for about 13seconds.

The wiping article has the measured values of Average Peak to PeakDistance, the Average Height Differential, and the Surface TopographyIndex, as set forth in Table I.

Comparative Example A

Comparative example A illustrates a nonwoven sheet having a uniformbasis weight that is essentially planar. The sheet is commerciallyavailable from Kao Corporation, Tokyo, Japan, as QUICKLE®.

TABLE I Average Height Average Peak to Surface Differential PeakDistance Topography Example # (mm) (mm) Index 1 0.74 1.5 0.5 2 1.8 3 0.6Comparative A 0.14 0.85 0.16

What is claimed is:
 1. A macroscopically three-dimensional cleaningsheet comprising: a nonwoven substrate, said substrate having a firstoutward surface and a second outward surface, wherein at least one ofsaid outward surfaces has a macroscopic three dimensional pattern, saidmacroscopic three dimensional pattern being defined by peaks and valleyssuch that said patterned outward surface has an Average Peak to PeakDistance of at least 1 mm, an Average Height Differential of at least 1mm, wherein said nonwoven substrate is made of fibers; and an additivedisposed on at least one of said outward surfaces, said additivecomprising at least one of a wax and/or an oil, wherein said additivecomprises mineral oil and microcrystalline wax mixed in a weight ratioof about 1:99 to 3:7.
 2. A cleaning sheet according to claim 1 whereinsaid average height differential is from 1 to 3 mm.
 3. A cleaning sheetaccording to claim 2 wherein said additive further comprises syntheticwax.
 4. A cleaning sheet according to claim 1 wherein said additive isadded at an add-on level from about 0.5 to 20 weight percent.
 5. Acleaning sheet according to claim 1 wherein said additive comprises atleast 1, but less than 6 weight percent of said cleaning sheet.
 6. Amacroscopically three-dimensional cleaning sheet comprising: a nonwovensubstrate, said substrate having a first outward surface and a secondoutward surface, wherein at least one of said outward surfaces has amacroscopic three dimensional pattern, said macroscopic threedimensional pattern being defined by peaks and valleys such that saidpatterned outward surface has an Average Peak to Peak Distance of atabout 3 to about 16 mm, an Average Height Differential of at least 1.5mm, wherein said nonwoven substrate is made of fibers; and an additivedisposed on at least one of said outward surfaces, said additivecomprising a microcrystalline wax mixed with a mineral oil.
 7. Acleaning sheet according to claim 6 wherein said Average Peak to PeakDistance is about 4 to about 12 mm.
 8. A cleaning sheet according toclaim 7 wherein said additive is substantially uniform over a continuousarea of said substrate.
 9. A cleaning sheet according to claim 8 whereinsaid nonwoven substrate is made of fibers having a denier of less than2.0 grams, per 9000 meter of fiber length.
 10. A cleaning sheetaccording to claim 3 wherein said additive further comprises a naturalwax.
 11. A cleaning sheet according to claim 6 wherein said additivecomprises at least 0.1 weight percent of said sheet.